1. Field of Invention
The present invention relates in general to the electrical connector field. More particularly, the present invention relates to the assembly of electrical connectors incorporating an interposer having a resilient wire bundle that provides a conductive path between two substrates and that is captured within an aperture of the interposer by a retention member. The present invention also relates to apparatus involved in the assembly of such electrical connectors.
2. Background Art
Electrical connectors are in widespread use in the electronics industry. In many computer and other electronic circuit structures, an electronic module such as a central processor unit (CPU), memory module, application-specific integrated circuit (ASIC) or other integrated circuit, must be connected to a printed circuit board (PCB). In connecting an electronic module to a PCB, a plurality of individual electrical contacts on the base of the electronic module must be connected to a plurality of corresponding individual electrical contacts on the PCB. This set of contacts on the PCB dedicated to contacting the electronic module contacts is known as a land grid array (LGA) site. Rather than permanently soldering the electronic module contacts to the LGA site, it is desirable to use LGA connectors that allow the electronic module to be installed to and removed from the LGA site. LGA connectors are also known as sockets, interconnects, interposers, carriers, and button board assemblies.
LGA connectors provide the user with the flexibility to upgrade or replace electronic modules during the manufacturing cycle and in the field. A trend in the electronics industry has been to increase both the quantity LGA sites and the density of each LGA site, i.e., the number of contacts per unit area at the LGA site. Another trend in the electronics industry is to reduce the rated insertion force necessary to insert the electronic module into the LGA connector.
One type of LGA connector that has proven to be very reliable incorporates resilient wire bundles. Electrical connectors having resilient wire bundles for providing conductive paths between two electronic substrates, i.e., an electronic module and a PCB, are well known to those skilled in the art. Such resilient wire bundles are also well known as wadded wire, fuzz buttons, button contacts, button wads, or contact wads, which are collectively referred to hereafter as resilient wire bundles.
For example, U.S. Pat. No. 6,062,870 to Hopfer, III et al., the disclosure of which is incorporated by reference herein, discloses an electrical interconnect that incorporates resilient wire bundles that are retained in holes of a carrier by compressive frictional engagement with a central section of the side wall of each of the holes. In use, the carrier is placed between two circuit boards and the resilient wire bundles provide conductive paths between the two circuit boards.
A well known problem with electrical connectors that incorporate resilient wire bundles is that one or more of the resilient wire bundles may be jarred loose and fall out from the interposer during transit or handling. If a resilient wire bundle is missing from the interposer, an open circuit will result when the interposer is used to connect two electronic substrates. In this case, the interposer that is missing the resilient wire bundle must be replaced for the two electronic substrates to be properly connected. Such opens occur notwithstanding the teachings of Hopfer, III et al. that the resilient wire bundles are force fitted into holes in the interposer. In a related problem, instead of being jarred completely out of the interposer, the resilient wire bundle is instead jarred partially loose from the interposer such that when the resilient wire bundle is compressed between the two electronic substrates, the resilient wire bundle bends over and makes contact with an adjacent resilient wire bundle or an adjacent contact on the electronic substrate. If a bent-over resilient wire bundle makes such an inadvertent contact, a short circuit will result. Such a short can catastrophically damage to one or both of the electronic substrates being interconnected. Accordingly, the interposer that contains the bent-over resilient wire bundle, and possibly also one or both of the electronic substrates being interconnected, would have to be replaced.
These problems are recognized in U.S. Patent Application Publication No. 2004/0002233 A1 to Advocate, Jr. et al., the disclosure of which is incorporated by reference herein, which discloses a method of assembling an interconnect device assembly which consists of cylindrical resilient wire bundles captured with a carrier. The interconnect device assembly is placed in a fixture and the ends of the resilient wire bundles are deformed by shaping dies in the fixture so that the resilient wire bundles now have a dog bone shape. The dog bone shape of the resilient wire bundles prevents the resilient wire bundles from being partially or totally dislodged during handling and transit. However, one or more of the shaping dies may insufficiently deform the resilient wire bundles and thereby fail to prevent same from being dislodged. Also, the shaping dies may inconsistently deform the resilient wire bundles (i.e., some shaping dies will under-penetrate the resilient wire bundles while other shaping dies will over-penetrate). The resulting unequal resilient wire bundle height increases the likelihood that one or more open circuits will occur when the resilient wire bundles are compressed between two electronic substrates. In this case, the interposer that contains the resilient wire bundles of unequal height must be replaced for the two electronic substrates to be properly connected.
Another problem with electrical connectors that incorporate resilient wire bundles is that the strands of the resilient wire bundles are not very robust. For example, the strands of resilient wire bundles are prone to spreading or “mushrooming” upon repeated insertions. If a resilient wire bundle is sufficiently mushroomed, an open circuit or near-open circuit will result when the mushroomed resilient wire bundle is subsequently compressed between two electronic substrates. This occurs because mushrooming can undesirably limit the compressive force on the resilient wire bundle and thereby increase electrical resistance through the resilient wire bundle to the point where an open circuit or near-open circuit is created. In this case, the interposer that contains the mushroomed resilient wire bundle must be replaced for the two electronic substrates to be properly connected. Moreover, the strands of resilient wire bundles can snag on mating features during insertion and withdrawals. If either a snagged strand of a resilient wire bundle or a mushroomed resilient wire bundle subsequently makes contact with an adjacent resilient wire bundle or an adjacent contact on the electronic substrate, a short circuit will result. Such a short can catastrophically damage to one or both of the electronic substrates being interconnected. Accordingly, the interposer that contains the snagged strand or mushroomed resilient wire bundle, and possibly also one or both of the electronic substrates being interconnected, would have to be replaced.
It should therefore be apparent that a need exists for an enhanced mechanism for connecting two substrates using resilient wire bundles.